I am studying a combined bachelor of engineering (electrical) and bachelor of mathematics; I just started this year and will graduate in 2018. The reason why I am doing double degrees and not a single degree is because I love both electrical engineering and mathematics and I could not ignore any of them. So with this in mind, I am thinking of doing two PhDs when I graduate (one in electrical engineering and one in mathematics). Is this a good path or I should concentrate on only one of them?

You just started your double major. I think it's too early to plan PhD right now. Concentrate on your bachelor of engineering and bachelor of mathematics. Three years later, you'll have much better idea if you really want to do two PhDs. Then ask this question again.
– scaaahuFeb 21 '14 at 7:41

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I wouldn't worry about it. A surprise twist will land you in chemistry or music or something unrelated anyways.
– Jason CFeb 21 '14 at 10:33

I think in 2018 you may even want to do no phd at all
– UmNyobeFeb 21 '14 at 13:05

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You're asking for advice on a course of action without stating what your goal is. If I asked you "should I take the bus?" I hope you would point out that you don't know where I want to go. Do you want to have a career in academia? Do you want to have a career in industry? Do you want to have a lot of certificates on your wall? What's your goal?
– Eric LippertFeb 21 '14 at 18:38

18 Answers
18

I suspect that most people who ask about the possibility of doing multiple PhDs are missing something fundamental in what a PhD is and what it's for. This is an understandable misperception because the general populace knows little about what PhD programs are all about, to the extent that even most people who enroll in a PhD program think they know what they're getting into and then find out that what they had in mind is an approximation to the truth (sometimes a good approximation and sometimes not).

In the various fictive media (novels, comic books, television, film...) having multiple PhDs -- often in confluence with a very youthful persona or explicitly pointed out that they were attained at an early age -- is a standard trope for a certain type of characterization: depending upon the genre it can signal super-genius types, intellectuals, or nerdy/socially awkward types. For instance, Professor Charles Xavier graduated from Harvard at the age of 16, and he holds PhDs in Genetics, Biophysics, Psychology, and Anthropology as well as an MD in Psychiatry. This is obviously meant to be a real-world grounding for his vast mental powers. On the TV show House, the youthful medical student Martha Masters has previously attained PhDs in applied mathematics and art history, and the characterization is less positive: they are not trying to suggest that she's a genius per se -- House is the genius! -- but rather that she has an extremely overachieving personality type.

Of course, Charles Xavier and Martha Masters are fictional characters. Moreover I imagine they were written by people who are not so familiar with PhD programs. In real life, having PhDs in Genetics, Biophysics, Psychology and Anthropology is not the hallmark of a super-genius: rather it would mean that the person is pathologically obsessed with graduate study. PhD's are not merit badges -- more of them is not better. Rather a PhD is the necessary and grueling training for a specific type of professional career.

If you are interested in a subject then you read and learn about it. You get a PhD in a subject because you want that subject to be an essential part of your career (which of course ought to imply that you are very interested in the subject). Moreover, although the PhD provides specific technical training in a certain subject, it does not provide exhaustive training: in most cases people spend the rest of their careers continuing to train in these areas. Rather the point of a PhD is to give you enough specific training so that you can henceforth direct your own training and learning. Otherwise put, a lot of what you do in a PhD is learning how to learn. But learning how to learn is actually a rather robust and subject-independent skill. If you learn how to learn genetics, then if later on your interests turn to psychology or biophysics you will be in a much different and better position to train yourself in these areas. In some ways, doing a PhD in one of these subjects and then turning around and doing another is like becoming an internet millionaire who wakes up one day and decides that she wants to sell electronics...so she shuts down her website, gives all her money away, and starts the business out of her parents' basement. (Or maybe it is like what happens in some of my dreams: I am doing high school all over again, and somehow it is not going as well as it did the first time around.) Why are you starting over from scratch?!?

It is true that "academic transfer" makes better sense between some fields than others. If Martha Masters got a PhD in art history and then decided that she wanted to do applied mathematics instead then she would not have been able to "segue" from one field to the other: she would indeed have had to go back to school. But that makes her story a bit sad: getting a PhD is very difficult and very time consuming, but it is not really a feat of strength, and getting two PhDs in two unrelated areas does not show how much of a super genius you are; it shows that you really changed your mind considerably about what you wanted to do with your life and maybe wasted a lot of your time. No matter how smart you are, I don't see how you can get a PhD in art history and then one in applied mathematics without spending at least eight years. You can't just skip to the end and pass the thesis defense by virtue of your preternatural brilliance: there is coursework, residence requirements, and various other mandatory things which necessarily take time. Her character is comic-booky: it is not really plausible that she could have these two degrees and have gone on to be a medical student while still being in her 20's, no matter how brilliant. [Well, "no matter how brilliant" is a little too strong: if she had graduated college at age 16, then the math works out okay...] Moreover, for someone who is that brilliant it would really be sad that she can't seem to figure out anything else to do besides infinite schooling.

Electrical engineering and mathematics are rather closely allied fields. For sure do a PhD in one or the other. While doing a PhD in either one you can choose the amount of involvement you have in the other field, i.e., you can do a very mathematical electrical engineering PhD or a math PhD on a mathematical topic with important applications in electrical networks. Then after you get your PhD you can continue to learn and train in one or both fields as you see fit. It is entirely plausible that you could land an academic job in one department while having gotten your PhD in the other department. This is an ambitious goal, but any academic job is an ambitious goal. Getting the second PhD is unlikely to be directly helpful once you have it, let alone worth the sacrifice of 4-6 years of your life!

Added: By the way, when you mention "mathematics" and "electrical engineering": I think of Raoul Bott, a brilliant and beloved professor whose long career at Harvard ended while I was studying there. I think that his story will be inspirational for many people with this confluence of interests. Check out his bio: he balanced his early interest in these two fields nicely...and only needed one PhD.

Really nice answer, wish I could give +1 for the very insightful answer that is, and +1 for learning to learn. Alas a single upvote is all I can do :)
– posdefFeb 21 '14 at 9:35

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@MNRC: Unfair to whom? To a fictional character? To all women everywhere?!? "Why can't a woman be seen as simply a genius who pursued her passions rather than an "overachiever"?" They can; no one has claimed otherwise. Nothing that I said about Martha Masters is in any way gender-specific.
– Pete L. ClarkMay 2 '15 at 7:47

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" It is sexism when a man who holds many PhDs is considered a "genius" while a woman just "lacks understanding". But that is not at all what I said. I said that if we were to take Professor X's multiple PhDs seriously we would regard him as being pathologically obsessed with graduate study. I also said that writers gave him multiple PhDs so as to try to indicate that he is a super genius. They also did this in many other, more convincing ways: e.g. by having him design ridiculously futuristic machinery.
– Pete L. ClarkMay 4 '15 at 0:11

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@MNRC: I don't understand why you put quotation marks around hurt your feelings. That's not a direct quote. Apologizing for hurting my feelings is not the same as apologizing for "hurting my feelings". Which is it? Failing an actual apology I just don't think your comments are being made in good enough faith to continue the conversation. My last word on the matter is as follows:
– Pete L. ClarkJul 1 '15 at 6:37

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It is distressing for an anonymous person to accuse a professional academic posting under his own name of sexism in this manner. I have mentored female academics at all levels and spoken passionately in defense of gender equality. Who are you? What have you done for women in academia? I have been working to promote equality for female students and academics in the real world. You are criticizing me for the fact that I am not describing the depictions of a television doctor on equal terms as a comic book superhero. That's just not reasonable enough to merit further response.
– Pete L. ClarkJul 1 '15 at 6:41

The work you do in a PhD is so specific and focused that I guarantee it will "ignore" most of mathematics and most of electrical engineering. Matt Might has a great illustration of this: PhD school in pictures

By the time you finish your current degree, you'll have a better idea of what specific area (i.e., subfield) of research you are most interested in (if you still want to do a PhD at that point). Then, decide whether it would be more at home in a mathematics or EE department, and apply to grad school accordingly.

Are you also interested in getting two jobs or having two families simultaneously? At some point in life people make decisions, long-term decisions that chart out a path for their lives.

The fact that you love both subjects is nothing but positive, and the fact that you have the drive and will-power to pursue higher education in both is admirable. It really is... But here I have lay out some points to consider:

Is it possible to do a PhD in two disparate fields simultaneously: probably.. I reckon it depends on the faculty/university and what they are willing to accept. Normally you can't get two PhDs from the same faculty (at least here it is not possible) and again, normally, universities do not accept other professional commitments while doing doctoral studies (with the exception of medical reasons). That is especially the case if you are officially employed as a grad student and not on stipends.

Is it advisable to go for two PhDs in disparate fields simultaneously: no, probably not. Doing a PhD alone is challenging, and I don't mean "OMG, it's too much work" but rather "OMG, wtf am I doing here!" or "OMG what am I gonna do with my life?!". Don't believe me? Just look at the most voted questions here, a healthy portion of them are about managing the mental burden of PhD studies.

Have you considered doing a cross-disciplinary PhD where you get to play with both subjects, meld them in a pot and make something awesome out of it? ;)

+1 except for "Is it advisable to go for two PhDs in disparate fields simultaneously: no, probably not." I would say definitely, absolutely, 100% not. Nobody will fund you to do two simultaneous PhDs, nobody will agree to advise one of two simultaneous PhDs, nobody has the time or energy to do two simultaneous PhDs.
– David RicherbyFeb 21 '14 at 9:35

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@DavidRicherby I full-heartedly agree with you, just didn't want to rule out the possibility of such a person existing out there. I mean there are... what, like 7 billion people out there? :)
– posdefFeb 21 '14 at 9:37

Good point, though I'd describe a worse-odds-than-winning-the-lottery event as "almost certainly no" rather than "probably no". :-)
– David RicherbyFeb 21 '14 at 9:42

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There may actually be quite a few people with time and energy to do two simultaneous PhDs, but seems to be no valid reason to do two simultaneous PhDs. You do research in a narrow direction or a bunch of different directions. As a side effect of that research, you get a PhD in one discipline or the other, or a crossdisciplinary - it doesn't particularly matter, and you can choose. If you later believe that you should have had chosen otherwise, then you get another PhD in that discipline, but again that's more like a 'why not?' reason, and a side effect of research you already did anyways.
– PeterisFeb 21 '14 at 10:29

I'm on my second PhD, 40 years after the first one. My first one was in mathematics, and I worked as a university teacher in maths for many years. I agree with the general advice given here. A PhD is as much research training as anything else. In the course of it you work intensively in a specialised area and learn how to develop an achievable project that can be done in the time you've got. You will pretty much be living and dreaming your project. It would be very difficult to be so intensively involved in two completely unrelated projects at the same time.

In your case, see how your current course goes. If you're still enthusiastic about both fields, look around various universities and see where there are interesting projects across both areas - aiming to do one PhD, and then maybe a post-doc position of some kind, if things work out that way. I knew a guy who studied the applied maths/engineering of the very high-speed spinning machines used in the textile industry - weird instabilities could lead to disaster. Another project I came across involved applying image processing techniques that had been developed for astronomy to classifying microscopic images of cells for medical research. There are lots of interesting hybrid fields out there: the more engineering/physical side of robotics, remote sensing, aspects of fibre optics, the bionic ear and bionic eye - lots of innovative signal processing needed!

As for my second PhD, it is in fine art, but I'm writing computer programs to "evolve" artworks (not a new idea, but there's plenty of room for new work). I need to engage with the history of art and other aspects of the discipline, since I'm in an art school now, though one if my supervisors is in computer science.

After writing my answer, I started wondering whether anyone had in real life done a PhD in both mathematics and art history. So my eyes popped out when I saw this: it sounds very interesting! May I ask how you arranged to do a PhD in fine art but with a CS supervisor? That sounds...nontraditional, to say the least.
– Pete L. ClarkFeb 22 '14 at 1:25

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@PeteL.Clark: As far as I know Samuel Eilenberg only had one PhD (in mathematics, of course), but he was also a prominent expert on Asian art. Someone once told me that he sometimes consulted with galleries and museums who knew him as "Professor Eilenberg from Columbia" without realizing he was a professor of mathematics.
– Mark MeckesFeb 22 '14 at 9:06

It's too early for all that - it is impossible to know now what you will enjoy by the end of your first degree, and there is no bonus for deciding early. I started my Physics degree loving space and looking forward to rocket science, by the end I wanted to do theoretical quantum physics, and now I do scientific/numerical computing. If you enjoy Maths and EE, you may end up enjoying a specific part of EE, like signal processing or quadrotor flight algorithms, etc.

You won't want to do a second PhD - A PhD is characterised by a lot of legwork, a lot of self-discovery and usually a capitulation to reality over hope in order to get something finished for the thesis. The important parts of that are not worth repeating. The only time a second PhD is worth doing is if you realise after completing one that you want to do research in another field, and that you can't make a path from one field to the other. A PhD is essentially the first step on a research path in a particular field, so make sure it's a field you want to do research in.

What happens after the PhD(s)? - A doctorate is just a step on a path to being a researcher, a lecturer, a professor. It is often the last piece of education people do just for the sake of a qualification. Afterward, if you go into research, you will have to choose a field, closely related to your PhD topic. You cannot go into two fields; the closest is to go into an interdisciplinary area between the two, hence quadrotor flight algorithms or sigproc. If you don't go into research, some experience of work would be a far better qualification for your CV than a second PhD.

My advice - Spend your current degree exploring the different fields. When you're intrigued by something in a course, follow it up with the lecturer, do some additional projects in your own time. Lecturers love people with enthusiasm and drive for a topic, and they will find time and resource for your project, perhaps with an eye to larger projects later. That process will be instructive, and help you understand what work you enjoy.

I realised I enjoyed numerical computing when I spent hundreds of hours expanding on a genetic algorithm project in my second year. Two years earlier, I wanted to build rockets. I would still like to build a rocket, but I would derive much of my enjoyment from simulation and design, rather than fabrication and testing; you will find that there are specific fields that match your skills and pique your interest, so accept that you will specialise, at least for a while.

"The important parts of that are not worth repeating." This is the best message. But it is a message that most students will not understand unless they have faced it themselves.
– mathreadlerMar 11 '18 at 10:01

Truthfully, there are few, if any, reputable universities that will allow you to pursue 2 PhDs at the same time. Also, most universities will not accept students who already have a PhD, especially when they overlap with one another.

It's barely even a good idea doing one PhD, let alone two! What you need to decide is what career you want. If it's to be a researcher, then doing a PhD is appropriate, because it is training to be a researcher. Once you have that career, why do another one, unless moving to a vastly different research area that requires very different research methodologies?

To add to some of the existing answers, a desire to do two PhDs in different fields may be a sign that you want to combine your interest and skills in those two areas. This is very reasonable. There are also arguably several better alternatives for combining two fields in a research career than completing two separate PhDs.

The main option is to do a PhD in one field that links in with the other field. With regards to the linking, you can have a PhD supervisor who works at the intersection of the two fields, you can get a co-supervisor who works in the second field, you can self-teach yourself the other field, or you can do formal training in the other field.

To make this discussion concrete, I can point to many examples where a person combines skills in one field to complement another.

I personally completed a PhD in psychology, but have endeavoured to acquire skills in statistics (through courses, self-teaching, a Post-Doc with a statistician, etc.).

I know a student who has a law degree and is completing a PhD in forensic psychology.

I knew a professor who had published books on music, and studied the psychology of music.

If after your undergraduate studies you find that you still enjoy engineering and mathematics, you may be able to find a PhD in one of these fields that links with the other.

An important difference between a bachelor's degree and a PhD is this: when doing a PhD, there is no maximum amount of effort one can usefully put in, nor is there a maximum level of attainment one can achieve. (Whereas with a bachelor's, once you have got top grades in all your courses, there's not much more you can usefully do.)

Supposing, what is very unlikely, that you have the academic ability and the huge amount of motivation and energy it would take to do two PhDs simultaneously. Then instead you should do one PhD, but:

in a shorter time than is usual

writing an astoundingly good thesis

publishing significant work

which you have largely done on your own

and having gained an exceptional depth of knowledge about your chosen field

For you to do all or most of this will be no more work than two simultaneous PhDs, but it will get you a lot further. Graduate students who do PhDs like this (they are quite a few) tend to quickly build prestigious and desirable careers for themselves, whereas 'professional students' who spend their lives amassing diplomas in different fields usually don't.

Well, I don't think its everybody's goal to get desirable careers. I know some people who do PhDs beside their works not because they need them, but just because they are interested in those areas, but not enough interested to leave their work and family to do a postdoc somewhere else
– user109595Jun 8 at 19:11

It is essentially impossible to do two PhD's concurrently, but if you like you can begin a second PhD after completing the first. Keep in mind that many people drop out of (even the first!) PhD, and are generally quite drained by the time the conclusion arrives.

One way, which might however be an opportunity for you, is to write an electrical engineering PhD that is very mathematical. Vice verse there are certainly many mathematical problems that arise from electricity question.

If you do this you will surely be able to study at both fields. Also, no matter what field you would choose, you would need to make sure that your thesis really belong to that field.

Definitely not. Try to concentrate on one first and do the other as a hobby. You will get a lot better because you don't have double-pressure. Alternatively, when you finished the first doctor degree work for several years (I'd say 10-20) and then you can possibly start with the other doctor degree.

In most cases you simply will not get offered the second PhD, even if you apply, and this remains true also if you try to do these two PhD positions in different countries. I am not aware if these are written rules, or unwritten rules, but, really, mostly no avail.

Probably there are some attempts to avoid a "professional PhD student" who would keep "studying" till retirement.

In my experience in the software industry, if your goal is to go into industry, a PhD often gives the impression of someone who is "overly academic". Someone who holds a doctorate may be seen as someone who preferred to stay in the comfort of academia. I imagine someone who had done two PhDs would be practically unemployable in the eyes of many hiring managers.

If your goal is to work in industry: I'd advise dedicating time to locating a company with highly skilled teams doing work that really interests you. Build relationships with those people and go work on those teams. I imagine working as a team on a real world project might be more enjoyable and inspiring than a PhD. You'll probably learn faster and broader too.

I do suggest completing your Bachelors first to see how you feel about progressing onto postgraduate studies. Having said that, I'm an individual who is completing two Masters degrees simultaneously. It may seem like an impossible task, but really it isn't.

Just like you I love both fields and really didn't think I should choose one over the other. I also work full-time (Executive position), and lead a pretty full life with sports, yoga, meditation, etc. It's all about knowing how to organize your time and still maintain balance.

So, if at the end of your Bachelors you feel you can do it, go for it. Why not? It's your life. The key is try to balance your life. You don't want to find yourself coming to a point where all you do is work and have no play. Then again, if you love your fields that much, work can be more like play. This isn't an impossible task at all. Passion for what you do, coupled with focus and organization are the key to your success. Really. Take it from me.

At the end of the day, do what feels right to you. You know what's best for you, not anyone else.

I have a PhD in Computational Biology. I have worked in that field, various engineering fields, am currently in management at a large corporation, and have even worked in finance. The point being, that once you have a PhD in a technical field, you generally have the credibility to switch fields to a number of other technical fields. It certainly takes some work to do so, but quite a bit less work that earning a second PhD.

Furthermore, about 80% of the process of getting a PhD is learning how to research and the other 20% is learning subject matter. This carries a couple different consequences in regard to pursuing a second PhD. First, while you could finish a second degree much faster than a first, there is a certain amount of structure to graduate school and you will invariably waste time developing (or rather proving that you have already developed) skills that you learned the first time around. Second, once you have the research background that a PhD confers, you can quickly learn the subject matter required to conduct novel research in a relatively similar field - it's not easy, but it's not that hard either.

First of all, in your case, it should be obvious that it is way, way too soon to even think about a PhD of any kind. In many ways even one PhD is too much these days - given the employment market today, opportunities for PhDs are slim to none. Best advice? Keep in mind that having a PhD often closes more doors than it opens.

Thank you for your interest in this question.
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